1. Field of the Invention
The present invention is directed to reed valve mechanisms for use in controlling fluid intake into and/or through fluid passages in internal combustion engines and in other fluid passages. More particularly, the present invention provides improved apparatus and method for constructing such reed mechanisms.
2. Background of the Prior Art
Presently it is common to employ various valve mechanisms to control air or air and fuel intake into and through internal combustion engines. The most widespread use of such valves today is a flexible "reed valve" which covers a port in a reed cage. The reed valve is attached at one of its ends to a base of the reed cage, allowing its unattached opposite end covering the port to be lifted away from the port. By orienting the reed cage in a downstream direction in the engine's air intake passage, when a negative pressure is present in the engine, the reed valve is flexed away from the reed cage port ant fluid is permitted to be drawn into the engine; when draw from the engine ceases, the reed valve shuts upon the port and fluid flow ceases.
The use of such reed valves is now standard on most crankcase compression two-stroke cycle engines both to control fluid intake and fluid transfer from the crankcase to the combustion chamber. Examples of such mechanisms are disclosed in applicant's U.S. Pat. Nos. 3,905,340, 3,905,341 and 4,051,820. More recently, similar reed valves have been utilized to improve engine performance in a variety of other applications, including in four-stroke cycle engines.
With the widespread use of reed valves, including metal and fiber composites, there has been considerable interest in finding ways to improve reed valve life and performance. One technique to improve reed valve life is to coat the reed cage with an elastomer, such as rubber or plastic, to provide a cushioned seat for the reed valve to strike on each cycle of the engine. In internal combustion engines, the use of such a cushioned seat is considered crucial to achieve adequate reed valve life from most conventional reed valves.
The conventional process for creating a cushioned reed valve seat is time consuming and expensive. Currently reed cage manufacturers must first arrange to have a recess provided in the reed cage surrounding each port in the reed cage. This is accomplished either by casting the reed cages with the recess or by machining the recess into the cage once the cage has been constructed. Once the recess is provided, the reed cage is then subjected to a complex coating process.
To coat the reed cage with rubber, generally two dies are furnished, one adapted to surround the outside of the recessed portion of the reed cage and the other inserted on the inside of the reed cage to prevent rubber from leaking into the interior of the reed cage. These dies must be carefully proportioned to assure exact fit and minimal leakage during rubber casting. Once the dies are in place, liquid rubber is injected under pressure into openings in the dies to fill the recessed portion of the reed cage.
After the rubber coating is applied, the rubber coating must then be planed or machined down to provide a smooth valve seat surrounding each port. If machining is not performed exactly or if too little rubber has been provided (e.g. as the result of air pockets), an uneven surface may be created which will lessen engine performance and may cause premature wear and deterioration of the reed valves.
Another come-on problem emerges if the dies do not exactly fit the reed cage. In these instances, the rubber will spread well beyond the recessed portion of the reed cage and require additional machining work for preparation of the valve cage. Evidence of such rubber leakage is commonalty seen on production reed cage units.
The entire procedure is extremely exacting and very expensive, costing on the order of approximately $14.00 per valve for low volume production and no less than approximately $3.00 per valve for very high volume production. These costs severely restrict the use of rubber coated valve seats to only higher cost applications, making it unrealistic to coat inexpensive reed cages such as reed plates in air compressors.
The molding process itself also tends to limit the type of valves which may be rubber coated. Reed cage designs which do not readily permit the insertion of a die or machining equipment into the interior of the reed cage, such as the aeroform reed cage disclosed in applicant's U.S. Pat. No. 4,879,976, cannot be rubber coated using this process without employing even more precise dies. Although it is possible to rubber coat these units by using a die which only mounts on the outside of the cage and includes projections which exactly fit within each port in the reed cage to prevent leakage into the interior of the reed cage, this process has design tolerances which are so demanding that full production quantities are not: practicable.
In response to the restrictions and high costs of this procedure, a number of other solutions have been implemented. In U.S. Pat. No. 4,696,263, applicant disclosed that the reed valves themselves may be rubber coated to improve life and performance. It has been found that reed valves constructed using this technique will perform as well or better against an uncushioned reed cage as conventional reed valves will perform against a rubber coated reed cage. However, if these rubber coated valves are combined with a properly constructed rubber coated reed cage, exceptional reed valve life can be expected.
Other procedures which have been implemented to avoid premature reed valve failure include techniques for improving flow through the reed cage itself, such as is disclosed in applicant's U.S. Pat. No. 4,879,976, and various modifications to basic reed valve design to limit stresses on the reed petals, such as is disclosed in applicant's U.S. Pat. No. 5,036,806. Despite the successes with these strategies, a cushioned reed cage remains highly desirable for maximum reed valve life.
Various attempts to create a less expensive cushioned reed cage also have been explored over the years. A number of patents have apparently described applying an independent layer of elastomer directly to a reed cage in order to cushion the reed valve. In U.S. Pat. No. 3,286,728 to Stephenson, issued Nov. 22, 1966, it is suggested to apply a layer of elastomer alone to a single face of a reed cage in order to create a cushioned reed valve seat. The precise method of attachment of the elastomer is not addressed in this patent. U.S. Pat. No. 4,633,825 to Flaig, issued Jan. 6, 1987, similarly teaches that a single layer of elastomer alone may be applied to each face of a non-recessed reed cage to provide a cushioned reed seat. A grommet is employed no assist in holding the elastomer layer in place on the distal end and the reed valve mounting hardware is used to hold the reed valve members and the elastomer in place on the base end.
In a somewhat different application, U.S. Pat. No. 4,082,295 to Bainard, issued Apr. 4, 1978, shows use of a reed valve to control fluid flow between crankcase chambers of a multiple cylinder two-stroke cycle engine and an elastomer seal attached to the reed valve seat to seal against the crankshaft. In that patent it is suggested to employ a rubber coating on a metal substrate as a non-recessed reed valve seat, with a mounting bolt passing through a reed valve and the reed valve seat to hold the entire unit together. Although it is not shown, that patent also suggests employing a similar non-recessed, rubber coated metal reed valve seat in other reed valve construction, such as that shown in the Stephenson patent.
Although the apparatus disclosed in the above patents may function adequately, further significant improvements are believed possible in reed cage construction. First, although a number of the above patents suggest avoiding a recessed reed cage, a recessed reed cage is believed to be important for proper reed valve performance. Second, none of the above patents is believed to provide a fully adequate method of mounting a separate elastomer layer to the reed cage. Among the probable problems are: the fragile nature of a non-reinforced elastomer layer; and insufficient and/or overly complicated methods of mounting the elastomer layer.
Accordingly, it is a primary object of the present invention to provide a method of construction of a reed valve mechanism for use in an internal combustion engine which supplies a cushioned reed valve seat at minimal manufacturing cost and effort.
It is a further object of the present invention to provide such a reed valve mechanism with a smooth and even valve seat without the need for machining of the cushioned surface.
It is an additional object of the present invention to provide such a reed valve mechanism which optimizes reed valve life and performance by reducing stresses on the reed valve members while assuring proper reed valve operation.
It is another object of the present invention to provide such a reed valve mechanism which is easily and efficiently constructed, with minimal expense and complication.
It is yet another object of the present invention to provide such a reed valve mechanism which may be easily implemented with other advances in reed valve technology to deliver even greater performance and reed valve life.
A still further object of the present invention is to provide a cushioning member for reed valves which may taper uniformly upward from the base of the valve cage to the apex thereof to allow more uniform seating of the reed valves.
These and other objects of the present invention will become evident from review of the following specification.